P0126 Mazda -the temperature gauge is just right at the middle, why does the engine light on?

Question

Light came on and off and back on again with same P0126 code

Answer 1

the themostat is stuck open, it is taking the car too long to warm up. 

if the it was stuck closed the car would overheat and the gauge would go up.

Replacing the thermostat is the first step, and reset the code. if the code comes back the engine coolant temp sensor might be bad or the wiring or worst case scenario the PCM